expect简单用法
在现今高度发展的it社会，已经有很多的自动化管理程序了，例如Puppet，Salt，func，Capistrano …….而且还有云虚拟化OpenStack,kvm,xen…..尤其Docker更是新生代黑马，为自动化管理而生的。但存在即为合理，你有高大上，我也有土肥圆，相对于快捷，简单的管理小批量linux机器，ssh和expect是非常好用的。
Expect是什么
他是一枚程序，是基于uucp（Unix to Unix Copy Protocol）的 发送/预期 的序列设计而来的。
The name “Expect” comes from the idea of send/expect sequences popularized by uucp, kermit and other modem control programs. However unlike uucp, Expect is generalized so that it can be run as a user-level command with any program and task in mind. Expect can actually talk to several programs at the same time. For example, here are some things Expect can do:
- Cause your computer to dial you back, so that you can login without paying for the call.
- Start a game (e.g., rogue) and if the optimal configuration doesn’t appear, restart it (again and again) until it does, then hand over control to you.
- Run fsck, and in response to its questions, answer “yes”, “no” or give control back to you, based on predetermined criteria.
- Connect to another network or BBS (e.g., MCI Mail, CompuServe) and automatically retrieve your mail so that it appears as if it was originally sent to your local system.
- Carry environment variables, current directory, or any kind of information across rlogin, telnet, tip, su, chgrp, etc.
Chat脚本由一系列expect-send对组成：expect等待输出中输出特定的字符，通常是一个提示符，然后发送特定的响应。例如下面的Chat脚本实现等待标准输出出现Login:字符串，然后发送somebody作为用户名；然后等待Password:提示符，并发出响应sillyme。
所以expect的工作流程是类似聊天的流程：
A跟B说 hello
B发现A跟他说hello，然后就回复hi然后A XXXXX然后B 发现A 在说XXXXX，所以就回复OOOOO.......
理解的话可以这样理解，虽然不够完整，但不失其意义。
然后既然知道了expect是怎么起作用的，那么的话就可以构思我们的自动化管理设计了，因为expect的设计原理就是为了去处理“交互式”，把“交互式”处理之后，人为的干预就少了,自然就实现自动化了。
一般的expect 使用
#!/usr/bin/expectset
timeout 5
spawn ssh 192.168.6.136 -p 1024
expect "password"
send "123passwd\r"
expect "Last login"
send " ifconfig |grep eth0 -A3\r"
expect eof
exit
- #!/usr/bin/expect是调用expect的写法，这个跟一般的shell 写 #!/bin/bash是不同的，这里的意义是以下内容是以什么方式运行，写expect就是expect的方式，写bash就是bash。
- spawn是创建一个进程，就是使用expect的时候是要运行expect进程的，spwan就是代表需要创建这样的进程的意思，理解为create也可以，这里就是创建一个ssh 连接的进程，后面的写法跟一般ssh连接执行命令无异。
- timeout 表示这个expect动作的生存时间，根据我的理解，例如设置为5秒，那么执行一次expect后就要等待5秒。
- expect eof和exit是指监测到eof就会执行exit，退出程序。
我们观察一般的ssh正常交互会有哪些情况，首次连接提示，成功连接后会生成knowhost，以后就不会提示了。
ssh 192.168.6.136 -p 1024
The authenticity of host '[192.168.6.136]:1024 ([192.168.6.136]:1024)' can't be established.
RSA key fingerprint is 7d:68:97:bc:f8:c1:b7:8a:a9:98:5a:03:4a:77:b9:eb.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '[192.168.6.136]:1024' (RSA) to the list of known hosts.
root@192.168.6.136's password:
正常连接提示：
ssh 192.168.6.136 -p 1024root@192.168.6.136's password:
连接被拒绝，可能是ssh没开，或者端口不对，或者iptables限制：
ssh 192.168.6.136 ssh: connect to host 192.168.6.136 port 22: Connection refused
没有连接地址：
ssh sadas
ssh: Could not resolve hostname sadas: Name or service not known
所以可以改成这样：
#!/usr/bin/expectset
timeout 5
spawn ssh 192.168.6.136 -p 1024
expect {
"Connection refused" exit
"Name or service not known" exit
"continue connecting" {send "yes\r";exp_continue}
"password:" {send "123passwd\r";exp_continue}
"Last login" {send " ifconfig |grep eth0 -A3\n"}}
expect eof
exit
- 将所以的expect收集为一个，然后使用类似switch-case的模式，匹配哪个就触发哪个，并且需要执行下一步动作的则需要加上exp_continue，其实这里就跟普通程序里面的控制循环的continue是一样的用法的。
[root@localhost test_shell_expect]# ./test3.sh
spawn ssh 192.168.6.136 -p 1024
root@192.168.6.136's password:
Last login: Wed Feb 25 07:07:42 2015 from 192.168.6.127
[root@wohost ~]# ifconfig |grep eth0 -A3
eth0 Link encap:Ethernet HWaddr 00:0C:29:DE:E9:90
inet addr:192.168.6.136 Bcast:192.168.6.255 Mask:255.255.255.0
inet6 addr: fe80::20c:29ff:fede:e990/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
再高端一点点可以这样，支持变量定义和传参功能
#!/usr/bin/expect
set timeout 5
set pw "123passwd"
set host [lindex $argv 0]
spawn ssh $host -p 1024expect {
"Connection refused" exit
"Name or service not known" exit
"continue connecting" {send "yes\r";exp_continue}
"password:" {send "$pw\r";exp_continue}
"Last login" {send " ifconfig |grep eth0 -A3\n"}}
expect eof
exit
- set就是用来变量定义的，而传参的话就是使用一个lindex $argv 0 的方式，$argv是指参数项数组，lindex将参数项数组的列表生成出来，然后 0 代表的是使用第一个值，不过这里有个小疑问我还没有完全理解，就是参考debug模式可以看到argv[0] = /usr/bin/expect argv[1] = -d argv[2] = ./test3.sh argv[3] = 192.168.6.136 ，第一个值应该argv[0] = /usr/bin/expect才对，但是程序能够获取到192.168.6.136，我暂时的理解就是他读取的是我执行命令的第一个参数，例如./test3.sh 192.168.6.136，所以第一个参数就是192.168.6.136，如此类推。
./test3.sh 192.168.6.136
spawn ssh 192.168.6.136 -p 1024 root@192.168.6.136's password:
Last login: Wed Feb 25 07:11:17 2015 from 192.168.6.127
ifconfig |grep eth0 -A3
[root@wohost ~]# ifconfig |grep eth0 -A3
eth0 Link encap:Ethernet HWaddr 00:0C:29:DE:E9:90
inet addr:192.168.6.136 Bcast:192.168.6.255 Mask:255.255.255.0
inet6 addr: fe80::20c:29ff:fede:e990/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
然后配合shell做个循环就可以简单实现批量管理
[root@localhost test_shell_expect]# cat test2.sh
#!/bin/bashwhile read hostdo
./test1.exp $host
done <file.txt
[root@localhost test_shell_expect]# cat file.txt log test1.exp test2.sh test3.sh
[root@localhost test_shell_expect]# cat file.txt 192.168.6.136192.168.6.127
大功告成。
troubleshooting
- 打开debug模式，使用-d，可以方便调试并且观看expect的执行过程。
输出效果如下：
./test3.sh 192.168.6.136
expect version 5.44.1.15
argv[0] = /usr/bin/expect argv[1] = -d
argv[2] = ./test3.sh argv[3] = 192.168.6.136 set argc 1set argv0 "./test3.sh"set argv "192.168.6.136"executing commands from command file ./test3.sh
spawn ssh 192.168.6.136 -p 1024parent: waiting for sync byteparent: telling child to go ahead
parent: now unsynchronized from child
spawn: returns {7991}expect: does "" (spawn_id exp4) match glob pattern "Connection refused"? no"Name or service not known"? no"continue connecting"? no"password:"? no"Last login"? noroot@192.168.6.136's password:
expect: does "root@192.168.6.136's password: " (spawn_id exp4) match glob pattern "Connection refused"? no
"Name or service not known"? no
"continue connecting"? no
"password:"? yes
expect: set expect_out(0,string) "password:"
expect: set expect_out(spawn_id) "exp4"
expect: set expect_out(buffer) "root@192.168.6.136's password:"
send: sending "123passwd\r" to { exp4 }
expect: continuing expect
expect: does " " (spawn_id exp4) match glob pattern "Connection refused"? no
"Name or service not known"? no
"continue connecting"? no
"password:"? no
"Last login"? no
expect: does " \r\n" (spawn_id exp4) match glob pattern "Connection refused"? no
"Name or service not known"? no
"continue connecting"? no
"password:"? no
"Last login"? no
Last login: Wed Feb 25 07:14:06 2015 from 192.168.6.127
expect: does " \r\nLast login: Wed Feb 25 07:14:06 2015 from 192.168.6.127\r\r\n" (spawn_id exp4) match glob pattern "Connection refused"? no
"Name or service not known"? no
"continue connecting"? no
"password:"? no
"Last login"? yes
expect: set expect_out(0,string) "Last login"
expect: set expect_out(spawn_id) "exp4"
expect: set expect_out(buffer) " \r\nLast login"
send: sending " ifconfig |grep eth0 -A3\n" to { exp4 }
ifconfig |grep eth0 -A3
[root@wohost ~]# ifconfig |grep eth0 -A3
eth0 Link encap:Ethernet HWaddr 00:0C:29:DE:E9:90
inet addr:192.168.6.136 Bcast:192.168.6.255 Mask:255.255.255.0
inet6 addr: fe80::20c:29ff:fede:e990/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
